Technique enhances collagen's medical uses

WASHINGTON, Sep 02, 2005 (United Press International via COMTEX) -- A new method of modifying collagen -- a naturally occurring protein in the body -- could make it capable of delivering drugs, preventing clots and scar tissue from forming and controlling the shape of tissues grown in the laboratory to repair damaged parts of the body.

"With this process, we can make the collagen that's already found in the human body behave in new ways, including some ways that are not found in nature," said Michael (Seungju) Yu, a materials science professor at Johns Hopkins University Whiting School of Engineering who invented the technique with his colleagues at the university.

"Modified collagen can give us great new tools for treating injuries and illnesses," Yu said.

Collagen, the body's most common protein, helps the blood clot and provides the matrix cells use to build nerves, bones and skin. Collagen is non-toxic and rarely triggers rejection by the immune system, so it has been used in cosmetics and a variety of medical and scientific applications.

Up until now, scientists have altered collagen with intense heat, which can damage its protein structure, or chemical reactions that limit its use in people. But Yu's technique, which was presented this week at the American Chemical Society meeting in Washington, may help circumvent those limitations.

His technique involves mixing collagen with smaller molecules called collagen mimetic peptides at relatively low temperatures. Bioactive agents capable of enhancing collagen's medical uses can easily be attached to the peptides, and when peptides that have been treated in this manner are combined with collagen, they change the way it functions.

For example, collagen normally draws cells to its matrix to make the scar tissue that seals wounds shut and the clots that block blood flow from damaged vessels. If a chemical called polyethylene glycol is attached to the peptides, collagen will repel cells instead of attracting them, making it impossible for blood clots and scar tissue to form. This is desirable when there is a danger of clots blocking a vein or artery or scar tissue interfering with the growth of new nerve connections in a wound.

Collagen treated with polyethylene glycol could also be used to guide the shape and composition of tissue grown in a laboratory for repair purposes, such as skin grafts to cover burns. In the past, when researchers tried to bond polyethylene glycol directly to collagen, they were forced to use harsh chemicals that made the resulting mixture unsafe for human use. Combining collagen with collagen mimetic peptides has meant the difference between success and failure.

Other possible applications include attaching antibiotics to the peptides to help collagen-based bandages fight infection. Growth factors could be incorporated to help cells grow more quickly, and medicated collagen could be used to coat surgical tools so the medication is released directly onto tissue as it is cut or handled.

Dr. Joseph Vacanti, co-director of the Center for Regenerative Medicine and Technology at Massachusetts General Hospital and Harvard Medical School, told United Press International the research looked promising.

"This new work is intriguing and blends the hope that better biomaterials will improve our ability to fight abnormal tissue processes in the body and create better scaffolding for tissue engineering and regenerative medicine," Vacanti said.